The singers are among stars who gave up their twitter accounts, Facebook pages and curtailed activity on other social networking sites from last Wednesday (01.12.10) - World AIDS Day - to raise money for the Keep a Child Alive charity, which is spearheaded by Alicia and treats children affected by the disorder.
Justin marked his return to the internet by thanking supporters for their donations.
He tweeted: "Justin Timberlake is alive! We raised $1mil to help KCA fight AIDS. Thank you so much and never stop buying life! (sic)"
After the celebrities - which also included Kim Kardashian, radio host Ryan Seacrest, Usher, Jennifer Hudson and Lenny Kravitz amongst others - reached their goal yesterday (06.12.10) Alicia gave her thanks.
She said: "From the bottom of my heart, thank you to all of the fans, friends and artists who stood together for this cause and saved real lives.
"I am humbled by the outpour of support from everyone."
In less than a week $500,000 was raised from public donations before the figure was rounded up to the required $1 million by billionaire Stewart Rahr.
Leigh Blake, co-founder of the Keep A Child alive organisation, said: "Although we never expected to raise $1 million overnight, we are completely blown away that we were able to achieve our goal in less than a week.
"Over 3,600 people have joined the fight and sacrificed their own digital lives for this important cause, and we intend to continue this movement."